Lubricant composition



Patented Oct. 25,1949

UNITED STATES PATENT OFFICE LUBRICANT COMPOSITION tion of Delaware N Drawing. Application May 26, 1948, Serial No. 29,406

4 Claims.

The invention relates to lubricants for use in working into shape objects of magnesium and magnesium-base alloys. It more particularly concerns an improved method of lubricating the working surfaces of dies and forming tools used in working or forming an article of a magnesiumbase alloy into a desired shape at the usual hot working temperatures, as in die-drawing, forming, forging, extrusion, and spinning, in which operations it is desirable or necessary to provide a lubricant between the surface of the work and that of the tool used to shape the work.

Heretofore various methods of lubrication have been used and suggested for the service indicated, but insofar as we are aware there is no method commercially available that is satisfactory for the purpose when these operations are conducted at temperatures exceeding about 500 F. With conventional lubrication at temperatures of 500 F. and up, the worked surfaces become scored and the debris of the Working operation, that is, the spent lubricant and oxidic scale formed on the magnesium during the hot working, is oftentimes smeared into and becomes embedded in the surface of the metal, making its removal difficult if not impossible. Another disadvantage of conventional methods of lubrication in the working of magnesium is that the spent lubricant On the Worked article causes it to be easily corrodible upon exposure to humid atmospheres and other corrosive conditions which cause little, if any, corrosion in the absence of the lubricant residue.

It is a desideratum in the art to provide improved lubrication in the hot forming of magnesium and magnesium alloy articles. Accordingly, it is the principal object of the invention to provide improved lubrication for the surfaces involved in hot working an article of magnesium and magnesium-base alloys with forming tools without the disadvantages of conventional lubricants. Other objects and advantages will appear as the description of the invention proceeds.

We have discovered that comminuted aluminum in admixture with a potassium or sodium soap and an oily material consisting of either lard oil, peanut oil, or hydrogenated cottonseed oil provides a lubricating composition which possesses adequate thermal stability and lubricity at the elevated temperatures usually used in forming shaped articles of magnesium and its alloys. In addition, the spent lubricant is noncorrosive to the work and easily removable. The invention then consists of the improved lubricant and method of lubricating hereinafter more fully described and particularly pointed out in the claims.

In compounding the lubricant composition for use in accordance with the invention, there is used comminuted aluminum having a particle size of about 120 mesh to 400 mesh. Various aluminum powders of suitable mesh size are commercially available, in atomized and flake forms. The conventional flake forms which are used as the aluminum pigment in aluminum paints are to be preferred.

The soaps of potassium and sodium may be used, such as the palmitate and stearate of these metals, or mixtures of these soaps. Of these soaps we prefer to use sodium stearate.

The proportions of the aluminum, soap, and oily material may vary over a wide range, the most satisfactory proportions being about 50 to 70 parts (by weight) of the comminuted aluminum, 20 to 30 parts of the soap, and 10 to 20 parts of one of the aforementioned oily materials. Mixing is simply accomplished by stirring the ingredients together at ordinary temperatures in any convenient manner.

Illustrative examples of suitable compositions are the following:

Example 1 Parts Comminuted aluminum Sodium stearate 25 Hydrogenated cottonseed oil 10 Example 2 Parts Comminuted aluminum 65 Sodium stearate 25 Lard oil 10 Example 3 Parts Comminuted aluminum 65 Sodium stearate 25 Peanut oil 10 In using the lubricating composition it may be applied to the surface of either the work or the tool or both, as by brushing or painting these surfaces with the composition. If desired, the composition may be sprayed onto the surfaces to be lubricated. Spraying is facilitated by diluting the compositions with a suitable volatile thinner or diluent such as carbon tetrachloride, naphtha, and kerosene, which is vaporized by the heated work to be shaped. The diluent may be used in any desired proportion, as, for example,

3 up to to parts of thinner per part of the composition.

After the articles are formed, the spent lubricant may be removed by a short dip in a conventional aqueous alkaline cleaning solution containing a caustic alkali such as a 10 per cent solution of caustic soda in water. Sodium car'- bonate solutions may be used and a wetting agent added if desired. These solutions function best at or near their boiling points.

The effectiveness of the composition to lubricate in die-forming magnesium and its alloys is well demonstrated in drawing blanks of a magnesiumbase alloy sheet into cylindrical cups, as in the following tests, using a magnesium alloy having the nominal composition of 3 per cent aluminum, 0.3 per cent manganese, and 1 per cent zinc, the balance being magnesium. The blanks were 0.064 inch thick and 4.75 inches in diameter. These were drawn into cups about 1.5 inches inside diameter and about 3 inches long with conventional drawing apparatus, an example of which appears in U. S. Patent 2,396,218. In drawing the cup, the work was lubricated with compositions such as those given in the above enumerated examples, so that lubricant was placed upon the surfaces subjected to rubbing or frictional forces during the draw. In these tests each blank was heated to about 600 F., the lubricant applied, and then the lubricated blank was immediately drawn into the cup. In each instance the lubricant composition exhibited stability in that no significant amount of decomposition was evident. At least five blanks could be drawn without scoring before the drawing dies required cleaning. The drawn cups were rendered free of lubricant residue by a 30-second immersion in a solution made by dissolving by weight 5 parts of sodium hydroxide, 5 parts of trisodium phosphate, and 0.5 part of a wetting agent in 89.5 parts of water, followed by rinsing in water. Further, corrosion tests of similarly drawn and lubricated cups, in which the cups were subjected to the corrosive action of a 3 percent solution of salt in water by immersion therein for 16 hours before cleaning, revealed no corrosion resulting from lubricant residue.

Among the advantages of the invention are that the lubricant resists decomposition and va- 4 porization at elevated temperatures; adequate lubricity is obtained at all working temperatures up to at least 650 F. die-loading and scoring of the worked metal are overcome; spent lubricant is easily and readily removed without removal of any of the worked metal surface; and the corrodibility of the lubricated and worked metal surface is not increased by the presence of spent lubricant or products thereof remaining on the worked surface.

We claim:

1. A lubricating composition consisting of a mixture of 50 to '70 parts by weight of comminuted aluminum having a mesh size of 120 to 400; 20 to parts of a metallic soap selected from the group consisting of the palmitate and stearate of one of the metals, potassium and sodium; and 10 to 20 parts of an oil selected from the group consisting of hydrogenated cottonseed oil, lard oil, and peanut oil.

2. A lubricating composition consisting of a mixture of to '70 parts by weight of flake aluminum having a mesh size of 120 to 400; 20 to 30 parts of sodium stearate; and 10 to 20 parts of hydrogenated cottonsed oil.

3. A lubricating composition consisting of a mixture of 50 to parts by weight of flake aluminum having a mesh size of to 400; 20 to 30 parts of sodium stearate; and 10 to 20 parts of lard oil.

4. A lubricating composition consisting of a mixture of 50 to '70 parts by weight of flake aluminum having a mesh size of 120 to 400; 20 to 30 parts of sodium stearate; and 10 to 20 parts of peanut oil.

ROBERT L. DIE'I'RICI-I. RE XFO'RD W. WILLIAMS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,838,189 Rattigan Dec. 29, 1931 2,065,248 Smith Dec. 22, 1936 2,183,347 Campbell Dec. 12, 1939 2,403,238 Rosenstiehl July 2, 1946 

